“We will be killing our vulnerable parents and grandparents through public policy,” Teresa Wells, a nursing home administrator, said at a press conference Wednesday by a group called Second Thoughts, which has mobilized to stop the bill.

The two sides squared off in an emotional hearing before the legislature’s public health committee. The panel heard hours of testimony on the bill, which would allow physicians to prescribe a lethal dose of medication that a mentally competent, terminally ill adult could self-administer to end his or her life.

The concept has been raised in Connecticut before but this marks the first time lawmakers have convened a hearing on the matter.

“Certainly shortening a life is not for everyone,’’ Bill Meyer of Westport told the panel. “But people should have the option.”

In 1991, Meyer helped his father, who was 88 and suffering from cancer, end his life by slipping a plastic bag over his head. After speaking publicly about the experience, he was arrested on a charge of second-degree manslaughter; he received accelerated rehabilitation.

Meyer said he received scores of letters from people who had read about his case. “They wished they’d done what I did but they didn’t have the courage,’’ he said. “They had to live with watching someone go through a prolonged death.”

But critics of the proposal, including disability rights advocates, hospice workers and the Catholic church, said the measure lacks sufficient safeguards to guard against abuse. They worry vulnerable patients would be coerced into a decision to chose doctor-assisted suicide. Moreover, they say, the exact end of life is often unknowable, even for patients given a terminal diagnosis.

“Would it not be better to invest in truly compassionate care, to expand the availability of first class palliative medicine and enlarge the scope of hospice programs than to open the door to abuses and cross into the highly problematic, morally questionable territory of legalizing assisted suicide?” said James McGaughey, executive director of the state Office of Protection and Advocacy for Persons with Disabilities.

Sen. Edward Meyer, a Democrat from Guilford who is one of the measure’s chief proponents in the General Assembly, said the process will be tightly regulated. Only those patients with less than six months to live would be eligible and they must be certified by a physician to be mentally competent and able to administer the medication on their own.

“This bill has many, many safeguards ... to ensure that the decision that’s being made by the patient is competent and informed,’’ Sen. Meyer said.

But he said he is open to even more protections, such as requiring a waiting period following a patient’s diagnosis before a prescription for life-ending medication could be filled and mandating that a second physician certify the patient’s mental competency and diagnosis.

“We’ve come a long way in the United States with respect to dignity in dying,’’ Sen. Meyer said.

Rep. Peggy Sayers, a Democrat from Windsor Locks and a critic of the bill, questioned Meyer on why the proposal was even necessary. “Instead of going to a doctor to get approval for this, what’s the difference between going out and taking a whole bottle of Tylenol and maybe a little Jameson [Irish whiskey] and taking care of the job that way? Why do you need to involve someone else?” she asked.

“This bill is intended to bring about death with dignity in a very scientific, medical, professional manner,’’ Sen. Meyer responded, “and not something that’s self-prescribed that you hope works.’’

The bill has the support of the American Civil Liberties Union of Connecticut, several clergy members and Lucie McKinney, the widow of former U.S. Rep. Stewart B. McKinney. In a letter to lawmakers, Lucie McKinney said she watched her husband die “a long, slow, agonizing death from HIV/AIDS.”

“If only you could place yourselves in the shoes of one of those dying patients for just a few hours, your vote on House Bill 6645 would be made easy,’’ McKinney wrote.

If approved, Connecticut would join Washington and Oregon as states that permit doctors to prescribe medication enabling patients with terminal illness to commit suicide. Similar proposals are pending in Vermont and New Jersey but was rejected by voters in Massachusetts in a hotly contested referendum in November.

The prospect for passage of the bill in Connecticut this year are unclear. Public health committee co-chairwoman Terry Gerratana said she has lingering questions.

“If this bill does go forward here in the committee,’’ she said, “ I have concerns about much of the language.’’